[CallSiteSplit] Make sure we remove nonnull if the parameter turns out to be a constant.

[trentxintong]

Summary

We do not need nonull attribute if we know an argument is going to be constant.

[junbuml]

Thanks for handling this. Just curious if you see any issue with the non-null attribute in a constant ?

test/Transforms/CallSiteSplitting/callsite-split.ll

44 ↗

(On Diff #142330)

Can you move this in callsite-split-or-phi.ll where we run only callsite-splitting pass. Looks like you can also use just like i32* instead of %struct.bitmap*.

[trentxintong]

Address comments.

[trentxintong]

In D45608#1067141, @junbuml wrote:

Thanks for handling this. Just curious if you see any issue with the non-null attribute in a constant ?

Probably no problem other than it bloats the IR a bit with unnecessary attribute.

[trentxintong]

Remove empty lines.

[trentxintong]

Ping. Thanks.

[fhahn]

LGTM, with the test simplification. Unfortunately there is no easy way to prevent adding the unnecessary nonnull attribute in first place.

test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll

577 ↗

(On Diff #143492)

Do we need inttoptr here?

590 ↗

(On Diff #143492)

I don't think we need a complex callee2 function that's called here. Could you just use the existing callee function?

[trentxintong]

Simplify test. I could not get rid of the inttoptr though.

llvm/trunk/lib/Transforms/Scalar/CallSiteSplitting.cpp

for (auto &I : CS.args()) {
     ++ArgNo;
   }
 }
 
 static void setConstantInArgument(CallSite CS, Value *Op,
                                   Constant *ConstValue) {
   unsigned ArgNo = 0;
   for (auto &I : CS.args()) {
-    if (&*I == Op)
+    if (&*I == Op) {
+      // It is possible we have already added the non-null attribute to the
+      // parameter by using an earlier constraining condition.
+      CS.removeParamAttr(ArgNo, Attribute::NonNull);
       CS.setArgument(ArgNo, ConstValue);
+    }
     ++ArgNo;
   }
 }
 
 static bool isCondRelevantToAnyCallArgument(ICmpInst *Cmp, CallSite CS) {
   assert(isa<Constant>(Cmp->getOperand(1)) && "Expected a constant operand.");
   Value *Op0 = Cmp->getOperand(0);
   unsigned ArgNo = 0;

llvm/trunk/test/Transforms/CallSiteSplitting/callsite-split-or-phi.ll

BB2:
   br label %End
 
 End:
   ret i32 %p
 }
 
 declare void @dummy(i32*, i32)
 declare void @dummy2(i32, i32)
+
+; Make sure we remove the non-nullness on constant paramater.
+;
+;CHECK-LABEL: @caller2
+;CHECK-LABEL: Top1.split:
+;CHECK: call i32 @callee(i32* inttoptr (i64 4643 to i32*)
+define void @caller2(i32 %c, i32* %a_elt, i32* %b_elt) {
+entry:
+  br label %Top0
+
+Top0:
+  %tobool1 = icmp eq i32* %a_elt, inttoptr (i64 4643 to  i32*) 
+  br i1 %tobool1, label %Top1, label %NextCond
+
+Top1:
+  %tobool2 = icmp ne i32* %a_elt, null
+  br i1 %tobool2, label %CallSiteBB, label %NextCond
+
+NextCond:
+  %cmp = icmp ne i32* %b_elt, null
+  br i1 %cmp, label %CallSiteBB, label %End
+
+CallSiteBB:
+  call i32 @callee(i32* %a_elt, i32 %c, i32 %c)
+  br label %End
+
+End:
+  ret void
+}